The present invention relates to communications receivers, and more particularly to a bidirectional interface that allows an external device to be controlled by and/or to control a communications receiver such as a satellite or cable television receiver.
Digital transmission of television signals can deliver video and audio services of much higher quality than analog techniques. Digital transmission schemes are particularly advantageous for signals that are broadcast via a cable television network or by satellite to cable television affiliates and/or directly to home satellite television receivers. Examples of such schemes are the MPEG-2 data transmission standard and the DigiCipher.RTM. II standard proprietary to General Instrument Corporation of Chicago, Ill., U.S.A., the assignee of the present invention. The DigiCipher.RTM. II standard extends the MPEG-2 systems and video standards, which are widely known and recognized as transport and video compression specifications specified by the International Standards Organization (ISO) in Document series ISO 13818. The MPEG-2 specification's systems "layer" provides a transmission medium independent coding technique to build bitstreams containing one or more MPEG programs. The MPEG coding technique uses a formal grammar ("syntax") and a set of semantic rules for the construction of bitstreams. The syntax and semantic rules include provisions for demultiplexing, clock recovery, elementary stream synchronization and error handling. The syntax and semantics of the MPEG-2 transport stream are defined in International Organisation for Standardisation, ISO/IEC 13818-1, International Standard, 1994 entitled "Generic Coding of Moving Pictures and Associated Audio: Systems," recommendation H.222, incorporated herein by reference. It is expected that digital television transmitter and receiver systems will replace existing analog systems just as digital compact discs have largely replaced analog phonograph records in the audio industry.
An advantage of digital transmission techniques is that the television signals can be compressed using various well known compression techniques in order to free up bandwidth in the cable or satellite television spectrum. This bandwidth can be used to provide additional services such as video games (e.g. the Sega.RTM. channel), Internet access, automatic control of a video tape recorder or the like, and/or the communication of data (that may or may not be related to the television services) to an external device. Such additional services can provide, for example, an interim solution to the provision of multimedia and interactive television while future technologies that include a merger of television, telephone, and the personal computer (PC) are being developed. Another example of an external device that can take advantage of additional bandwidth is one which monitors what channels are being watched on a user's television, which is useful for monitoring viewership for ratings purposes. In order to successfully implement such external devices for providing additional functions to a consumer, it will be necessary to provide a communication path between the cable or satellite television receiver and the external device.
In particular, it would be advantageous to provide a low-cost, bi-directional serial data port on a communications receiver, such as a "set-top box" that receives television signals from satellite or cable television systems. Such an interface port would enable the communication of data between the communications receiver and one or more external peripherals, such as a personal computer, video player/recorder, video game console, or the like. It would be particularly advantageous if such an interface port enabled signals from the communications receiver to directly control the external device, or vice-versa. It would be still further advantageous to provide an interface that couples the external device to the user interface of the communications receiver. In this manner, an external device would have the ability to initiate functions that are typically controlled by a user.
One use for an interface that provides direct control between a communications receiver and an external device would be to allow a set-top box to receive a television program signal carrying identifying data, and to automatically command a video tape recorder to commence recording the program in response to the identifying data. Other uses would be to enable a video game console to command a set-top box to tune to a particular channel that is carrying a video game service, and to enable an Internet interface to command the set-top box to tune to an Internet access channel. Other uses for such an interface port will become apparent to those skilled in the art once they have knowledge of the present disclosure.
The present invention provides an interface having the aforementioned and other advantages.